procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
Set up a repo
$ cat <<EOF >> $HGRCPATH
> [ui]
> interactive = true
> [extensions]
> record =
> EOF
$ hg init a
$ cd a
Record help
$ hg record -h
hg record [OPTION]... [FILE]...
interactively select changes to commit
If a list of files is omitted, all changes reported by 'hg status' will be
candidates for recording.
See 'hg help dates' for a list of formats valid for -d/--date.
If using the text interface (see 'hg help config'), you will be prompted
for whether to record changes to each modified file, and for files with
multiple changes, for each change to use. For each query, the following
responses are possible:
y - record this change
n - skip this change
e - edit this change manually
s - skip remaining changes to this file
f - record remaining changes to this file
d - done, skip remaining changes and files
a - record all changes to all remaining files
q - quit, recording no changes
? - display help
This command is not available when committing a merge.
(use 'hg help -e record' to show help for the record extension)
options ([+] can be repeated):
-A --addremove mark new/missing files as added/removed before
committing
--close-branch mark a branch head as closed
--amend amend the parent of the working directory
-s --secret use the secret phase for committing
-e --edit invoke editor on commit messages
-I --include PATTERN [+] include names matching the given patterns
-X --exclude PATTERN [+] exclude names matching the given patterns
-m --message TEXT use text as commit message
-l --logfile FILE read commit message from file
-d --date DATE record the specified date as commit date
-u --user USER record the specified user as committer
-S --subrepos recurse into subrepositories
-w --ignore-all-space ignore white space when comparing lines
-b --ignore-space-change ignore changes in the amount of white space
-B --ignore-blank-lines ignore changes whose lines are all blank
-Z --ignore-space-at-eol ignore changes in whitespace at EOL
(some details hidden, use --verbose to show complete help)
Select no files
$ touch empty-rw
$ hg add empty-rw
$ hg record empty-rw<<EOF
> n
> EOF
diff --git a/empty-rw b/empty-rw
new file mode 100644
abort: empty commit message
[10]
$ hg tip -p
changeset: -1:000000000000
tag: tip
user:
date: Thu Jan 01 00:00:00 1970 +0000